Lintuzumab Ac-225

–  99.8% tumor growth inhibition achieved with a single dose of ATNM-400 in preclinical prostate cancer models –  ATNM-400 accumulated in tumors for up to 144 hours and showed minimal uptake in healthy tissues in prostate cancer xenograft model – Initial ATNM-400 preclinical data to be presented at AACR including results in Pluvicto resistant prostate cancer models NEW YORK, NY, USA I March 27, 2025 I Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a pioneer in the development of targeted radiotherapies, today announced ATNM-400, a novel, non-PSMA targeting, first in class radiotherapy for prostate cancer utilizing the Actinium-225 (Ac-225) radioisotope. Initial preclinical data from ATNM-400 will be presented at the American Association for Cancer Research (AACR) Annual Meeting being held on April 25 – 30, 2025, in Chicago, IL. The ATNM-400 AACR abstract will include the results from in vitro and in vivo studies including biodistribution imaging and efficacy analyses with various dose levels of ATNM-400. Actinium continues to advance ATNM-400 with additional data expected from Pluvicto-resistant prostate cancer models at AACR. Pluvicto (Lu-177-PSMA-617) is a prostate-specific membrane antigen (PSMA) directed targeted radiotherapy that uses the beta-particle emitting radioisotope Lutetitium-177 (Lu-177) that is approved for patients with metastatic prostate cancer. Pluvicto is marketed and sold by Novartis and generated sales of $1.39 billion in 2024. ATNM-400 is differentiated from Pluvicto as it targets a different marker than PSMA that has been shown to be overexpressed in patients with prostate cancer and uses the alpha-particle emitter Ac-225, which is more potent than Lu-177 but has a shorter path length, which could result in fewer off-target effects. Sandesh Seth, Actinium’s Chairman and CEO, said, “The current era of radiotherapy is built on the clinical and commercial success of Pluvicto in prostate cancer. The field is now looking to address patients that do not respond or progress after Pluvicto therapy. We believe ATNM-400 can address this high unmet need and we are incredibly excited by our data to date. As anticipated, we have seen robust tumor control and ATNM-400 has shown to be well tolerated in preclinical studies, which we believe is due to the precise and potent cell-killing of Ac-225. We are also highly excited by the results of our biodistribution studies that showed selective tumor uptake with minimal uptake in normal tissues. By focusing on a non-PSMA target, we also believe ATNM-400 has the potential to address some of the toxicities reported with Pluvicto and other PSMA targeting radiotherapies such as xerostomia. We are eager to present our ATNM-400 data at AACR and to continue to advance this highly novel prostate cancer candidate.” Highlights from the abstract include: ATNM-400 AACR Presentation Details Title: ATNM-400 is a novel Actinium-225 antibody radioconjugate with strong efficacy in preclinical models of prostate cancer Abstract Number: 578 Session: PO.ET08.01 – Theranostics and Radiotheranostics Date & Time: April 27, 2025 – 2:00 pm – 5:00 pm About Actinium Pharmaceuticals, Inc. Actinium is a pioneer in the development of targeted radiotherapies intended to meaningfully improve patient outcomes. Actinium is advancing its lead product candidate Actimab-A, a CD33 targeting therapeutic, as potential backbone therapy in acute myeloid leukemia (AML) and other myeloid malignancies leveraging the mutation agnostic alpha-emitter radioisotope payload Actinium-225 (Ac-225). Actimab-A has demonstrated potential activity in relapsed and refractory acute myeloid leukemia (r/r AML) patients in combination with the chemotherapy CLAG-M including high rates of Complete Remissions (CR) and measurable residual disease (MRD) negativity leading to improved survival outcomes and is being advanced to a pivotal Phase 2/3 trial. In addition, Actinium is engaged with the National Cancer Institute (NCI) under the Cooperative Research and Development Agreement (CRADA) for development of Actimab-A in AML and other myeloid malignancies. The first clinical trial under the CRADA will evaluate the triplet combination comprised of Actimab-A, Venetoclax (Abbvie/Roche) an oral Bcl-2 inhibitor and ASTX-727 (Taiho Oncology, an Otsuka holdings company) a novel oral hypomethylating agent (HMA) in frontline acute myeloid leukemia (AML) patients. Additionally, Actinium is developing Actimab-A as a potential pan tumor therapy in combination with PD-1 checkpoint inhibitors including KEYTRUDA ® and OPDIVO ® by depleting myeloid derived suppressor cells (MDSCs), which represents a potential multi-billion-dollar addressable market. Iomab-ACT, Actinium’s next generation conditioning candidate, is being developed with the goal of improving patient access and outcomes for potentially curative cell and gene therapies. Iomab-B is an induction and conditioning agent prior to bone marrow transplant in patients with r/r AML, which Actinium is seeking a potential strategic partner for the U.S. ATNM-400 is Actinium’s novel non-PSMA targeting Ac-225 radiotherapy for prostate cancer, which is supported by preclinical data and is being advanced to clinical trials. In addition, the company’s R&D efforts are primarily focused on advancing several preclinical programs for solid tumor indications. Actinium holds 230 patents and patent applications including several patents related to the manufacture of the isotope Ac-225 in a cyclotron. For more information, please visit: https://www.actiniumpharma.com/ SOURCE: Actinium Pharmaceuticals

- ATNM-400 is a novel, non-PSMA targeting, first-in-class Actinium-225 radiotherapy for prostate cancer with initial preclinical results to be presented at the AACR Annual Meeting - Actinium is establishing radiopharmaceutical manufacturing infrastructure in 2025 to support expanding clinical trials and to leverage its proprietary Actinium-225 cyclotron manufacturing technology - Data from several clinical trials expected in 2H:2025 across myeloid malignancies, solid tumors and cell and gene therapy conditioning - Actinium's targeted radiotherapy programs expanded to four multi-billion-dollar market opportunities NEW YORK, March 27, 2025 /PRNewswire/ -- Actinium Pharmaceuticals, Inc. (NYSE AMERICAN: ATNM) (Actinium or the Company), a pioneer in the development of targeted radiotherapies, today provided a business update detailing recent achievements and anticipated milestones from its revitalized and expanding clinical pipeline. The update featured the unveiling of ATNM-400, Actinium's new Actinium-225 (Ac-225) solid tumor program, which is a novel, non-PSMA targeting, first-in-class radiotherapy for prostate cancer. Initial preclinical data from ATNM-400 will be presented at AACR on April 27, 2025. In addition, Actinium highlighted its 2025 manufacturing infrastructure activity, including its Actinium-225 cyclotron manufacturing technology, to support its expanding clinical pipeline. Finally, Actinium highlighted several clinical trials that are expected to generate clinical data in the second half of 2025 including its Actimab-A frontline AML trial under its Cooperative Research and Development Agreement (CRADA) with the National Cancer Institute (NCI), data from trials in the Actimab-A solid tumor program which combines Actimab-A with PD-1 checkpoint inhibitors KEYTRUDA® and OPDIVO® in head and neck squamous cell carcinoma (HNSCC) and non-small cell lung cancer (NSCLC) and Iomab-ACT commercial CAR-T and sickle cell disease (SCD) trials. This update follows Actinium's company presentation at Trump Mar-a-Lago Club on March 26th and an Actimab-A KOL investor call on March 25th, which can be accessed for replay here. Sandesh Seth, Actinium's Chairman and CEO, said, "We are resurgent and expect 2025 will be an impactful year for Actinium as we execute to demonstrate the inherent value of our truly innovative and first of their kind clinical programs that focus on patients with high unmet needs. We are thrilled to introduce ATNM-400 and we look forward to presenting our promising preclinical results at AACR in April. We believe a significant opportunity exists in prostate cancer for ATNM-400, particularly for patients progressing or not well served by the PSMA targeting radiotherapy Pluvicto given its novel target and the potent cell killing ability of the Ac-225 isotope payload. In conjunction with advancing our clinical programs, several of which are expected to generate clinical data this year, we are building out manufacturing infrastructure in 2025 to support these programs which are expected to enter advanced development in 2026. Our strong balance sheet with cash runway expected to last into mid-2027 allows us to focus on unlocking the value inherent in our pipeline which has four distinct blockbuster opportunities with Actimab-A in hematology and solid tumors, Iomab-ACT in cell and gene therapy conditioning and now ATNM-400 in prostate cancer." Actinium's 2025 achievements to date including the following: Unveiled ATNM-400, a first-in-class, novel non-PSMA targeting Actinium-225 radiotherapy for prostate cancer with initial preclinical data to be presented at AACR on April 27, 2025 Initiated Actimab-A frontline AML triplet trial under NCI CRADA that will study Actimab-A as a backbone in combination with Venetoclax and ASTX-727, an oral hypomethylating agent developed by Taiho oncology, Inc., an Otsuka Holdings company Results of Actimab-A + CLAG-M combination trial published in the peer-reviewed journal Leukemia highlighting high rates of MRD- and improved overall survival in patients with r/r AML Initiated Actimab-A solid tumor program to combine Actimab-A with PD-1 checkpoint inhibitors KEYTRUDA and OPDIVO in head-to-head trials in head and neck squamous cell carcinoma and non-small cell lung cancer Entered into sponsored research agreements with Memorial Sloan Kettering Cancer Center to further elucidate Actimab-A's mutation agnostic mechanism of action and potential as a backbone therapy in myeloid malignancies Executed a supply agreement with Exckert & Ziegler for Actinium-225 Radioisotope to support comprehensive development activities for both U.S. and international clinical trials Abstracts accepted for presentation at the American Association for Cancer Research Annual Meeting highlighting Actimab-A's mutation agnostic profile in AML Actinium's pipeline revitalization has resulted in expanded market opportunities for its first-in-class targeted radiotherapies in myeloid malignancies, solid tumors and cell and gene therapy conditioning. Actinium seeks to address four distinct blockbuster opportunities with ATNM-400, Actimab-A and Iomab-ACT. Actinium outlined its 2025 business objectives for its revitalized and expanding clinical pipeline as follows: Pipeline Expansion into Prostate Cancer with ATNM-400, a first-in-class, non-PSMA targeting Ac-225 radiotherapy Present abstract at AACR highlighting Actinium-225 targeted radiotherapy for novel radiotherapy cancer target Establish In-house Radiopharmaceutical Manufacturing & Production Advance build-out of manufacturing facility Explore strategic partnerships leveraging proprietary Actinium-225 cyclotron manufacturing technology Actimab-A as a mutation agnostic, backbone therapy for myeloid malignancies including acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) across multiple treatment settings Initiate Phase 2/3 trial in combination with CLAG-M in relapsed or refractory AML and seek potential partners or collaborators Generate initial clinical data in frontline AML in first trial under CRADA with NCI Initiate additional clinical trials in myeloid malignancies Actimab-A as a pan solid tumor therapy in combination with PD-1 inhibitors including KEYTRUDA and OPDIVO by depleting myeloid derived suppressor cells (MDSCs) Generate clinical proof of concept data in head and neck squamous cell carcinoma and non-small cell lung cancer Explore additional solid tumor indications for future trials Iomab-ACT as a universal targeted conditioning agent to increase patients access to cell & gene therapies and improve patient outcomes Present initial data from commercial CAR-T trial at University of Texas Southwestern Generate clinical data in first non-malignant indication from sickle cell disease allogeneic stem cell transplant trial at Columbia University About Actinium Pharmaceuticals, Inc. Actinium is a pioneer in the development of targeted radiotherapies intended to meaningfully improve patient outcomes. Actinium is advancing its lead product candidate Actimab-A, a CD33 targeting therapeutic, as potential backbone therapy in acute myeloid leukemia (AML) and other myeloid malignancies leveraging the mutation agnostic alpha-emitter radioisotope payload Actinium-225 (Ac-225). Actimab-A has demonstrated potential activity in relapsed and refractory acute myeloid leukemia (r/r AML) patients in combination with the chemotherapy CLAG-M including high rates of Complete Remissions (CR) and measurable residual disease (MRD) negativity leading to improved survival outcomes and is being advanced to a pivotal Phase 2/3 trial. In addition, Actinium is engaged with the National Cancer Institute (NCI) under the Cooperative Research and Development Agreement (CRADA) for development of Actimab-A in AML and other myeloid malignancies. The first clinical trial under the CRADA will evaluate the triplet combination comprised of Actimab-A, Venetoclax (Abbvie/Roche) an oral Bcl-2 inhibitor and ASTX-727 (Taiho Oncology, an Otsuka holdings company) a novel oral hypomethylating agent (HMA) in frontline acute myeloid leukemia (AML) patients. Additionally, Actinium is developing Actimab-A as a potential pan tumor therapy in combination with PD-1 checkpoint inhibitors including KEYTRUDA® and OPDIVO® by depleting myeloid derived suppressor cells (MDSCs), which represents a potential multi-billion-dollar addressable market. Iomab-ACT, Actinium's next generation conditioning candidate, is being developed with the goal of improving patient access and outcomes for potentially curative cell and gene therapies. Iomab-B is an induction and conditioning agent prior to bone marrow transplant in patients with r/r AML, which Actinium is seeking a potential strategic partner for the U.S. ATNM-400 is Actinium's novel non-PSMA targeting Ac-225 radiotherapy for prostate cancer, which is supported by preclinical data and is being advanced to clinical trials. In addition, the company's R&D efforts are primarily focused on advancing several preclinical programs for solid tumor indications. Actinium holds 230 patents and patent applications including several patents related to the manufacture of the isotope Ac-225 in a cyclotron. For more information, please visit: Forward-Looking Statements This press release may contain projections or other "forward-looking statements" within the meaning of the "safe-harbor" provisions of the private securities litigation reform act of 1995 regarding future events or the future financial performance of the Company which the Company undertakes no obligation to update. These statements are based on management's current expectations and are subject to risks and uncertainties that may cause actual results to differ materially from the anticipated or estimated future results, including the risks and uncertainties associated with preliminary study results varying from final results, estimates of potential markets for drugs under development, clinical trials, actions by the FDA and other governmental agencies, regulatory clearances, responses to regulatory matters, the market demand for and acceptance of Actinium's products and services, performance of clinical research organizations and other risks detailed from time to time in Actinium's filings with the Securities and Exchange Commission (the "SEC"), including without limitation its most recent annual report on form 10-K, subsequent quarterly reports on Forms 10-Q and Forms 8-K, each as amended and supplemented from time to time. Investors: [email protected] SOURCE Actinium Pharmaceuticals, Inc. 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